On her best days, Amy Winehouse is a mess. The 24-year-old wears her hair in a beehive so large and teetering that it could hide the chorus of middle-aged black women that seems to materialize at the back of her throat whenever she sings. Having once thought herself overweight, Winehouse now keeps her body little-girl tiny and covered with enough tattoos to earn her cred at a medium-security prison. Onstage, she's known to favor poodle skirts. It's an aesthetic that takes some getting used to.

On her worst days—and there have been plenty of late—Winehouse looks a safe bet for an...